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I suspect the drop might be too much and your weight might be pitched too far forward.
I previously had the telescopic and it annoyed. My mate who is 6'4'' initially had the telescopic/'M' set-up and where I 6'3'' then the telescopic might be my friend.I also suspect your dealer is doing their best to satisfy your desired position.
Yes, test ride the flat bar, but just remember you might be comparing 'extended' vs 'telescopic'.I look forward to a pic of the JK mid-rise
YMMV
I'm 6'2'' and moved from 'M' to 'S'.
I really like it; I have a 580mm seatpost which I believe is the 'extended' seatpost. I like the drop position, but it depends on what position you like and how 'quite tall' and 'flexible' you are. I have the seatpost at its highest point, and if I don't extend it all the way which sometimes happens, I find it really annoying as I'm in 'chimp on a bike' territory.
Also this page might also point you in the right direction